[boost] [format] Allow the format library to use std::optional

Subject: [boost] [format] Allow the format library to use std::optional
From: Sean Farrow (sean.farrow_at_[hidden])
Date: 2019-03-30 15:14:18

Hi,

Would be possible/desired to allow boost.format to use std::optional instead of boost.optional when compiling a C++17 project.

I've raised a GitHub issue to resolve this:
https://github.com/boostorg/format/issues/63

I would be happy to do this if it were warranted.

Kind regards
Sean.